On the Transmit Beamforming for MIMO Wiretap Channels: Large-System Analysis

TL;DR

This paper analyzes the ergodic secrecy rates of MIMO wiretap channels in fast fading environments using large-system approximations, providing a practical method for covariance optimization with validated numerical results.

Contribution

It introduces a large-system analysis approach to approximate ergodic secrecy rates in MIMO wiretap channels, enabling efficient covariance optimization.

Findings

Large-system approximation closely matches simulated secrecy rates.

The approach facilitates practical covariance optimization.

Numerical results reveal key features of optimal precoders.

Abstract

With the growth of wireless networks, security has become a fundamental issue in wireless communications due to the broadcast nature of these networks. In this work, we consider MIMO wiretap channels in a fast fading environment, for which the overall performance is characterized by the ergodic MIMO secrecy rate. Unfortunately, the direct solution to finding ergodic secrecy rates is prohibitive due to the expectations in the rates expressions in this setting. To overcome this difficulty, we invoke the large-system assumption, which allows a deterministic approximation to the ergodic mutual information. Leveraging results from random matrix theory, we are able to characterize the achievable ergodic secrecy rates. Based on this characterization, we address the problem of covariance optimization at the transmitter. Our numerical results demonstrate a good match between the large-system approximation and the actual simulated secrecy rates, as well as some interesting features of the precoder optimization.